For a mechanical seal, which is an example of sliding component, to maintain sealing property for a long period of time, it must satisfy the mutually exclusive conditions of “seal” and “lubricate.” Particularly in recent years, the demand for lower friction is increasing further in the area of environmental protection, etc., as a means to prevent the sealed fluid from leaking while reducing mechanical loss at the same time. One way to reduce friction is to generate dynamic pressure between the sealing faces by means of rotation to create the so-called fluid lubrication state where the surfaces slide against each other with a liquid film in between. In this case, however, positive pressure generates between the sealing faces and the fluid flows from the sealing faces from the part subject to the positive pressure. This is the so-called lateral leak that occurs with bearings and corresponds to the sealing leak.
Traditionally in the field of so-called “inside type” mechanical seals, where the mechanical seal is comprised of a seal area separating a fluid to be sealed on the outer periphery side and atmosphere on the inner periphery side to seal the fluid on the outer periphery side, the one shown in FIG. 4 is known wherein, to reduce the frictional torque while offering good sealing performance, a tapered passage 53 that gradually widens toward the interior is provided on the inner periphery of a seal contacting area 50 of a stationary seal ring 51 and rotating seal ring 52, with a single or multiple spiral grooves 54 provided radially on the side of this passage 53 in such a way that one end of this spiral groove 54 contacts the inner periphery of the seal contacting area 50 (hereinafter referred to as “Prior Art 1”; refer to Patent Literature 1).
Also, traditionally in the field of sliding components used for so-called “inside type” mechanical seals, etc., the component shown in FIG. 5 is known which comprises: a first dam 61 provided on a sealing face 60 and forming a circular shape; a suction means 62 consisting of multiple dimples arranged in a circular pattern, where the dimples are narrow grooves inclined by a certain angle from the first dam 61 toward the sealed fluid side corresponding to a rotational direction; a discharge means 63 consisting of multiple dimples arranged in a circular pattern, where the dimples are narrow grooves inclined by a certain angle from the first dam 61 in the rotational direction opposite the one in which the suction means 62 is inclined; and a seal area 64 formed on the periphery face of the discharge means 63 on the opposite side of the first dam 61 (hereinafter referred to as “Prior Art 2”; refer to Patent Literature 2).
However, Prior Art 1 presents problems because the radial-direction width of the seal contacting area 50 is decreased and a tapered passage 53 that gradually widens toward the interior is provided on the inner periphery of the seal contacting area 50, with spiral grooves 54 provided on the side of this passage 53, where the first problem is that high surface pressure generates on the sealing face 50 to increase local friction, while the second problem is that the pumping effect of the spiral grooves 54 on the inner periphery side of the tapered passage 53 decreases.
On the other hand, Prior Art 2, which is designed with multiple dimples being narrow grooves inclined toward the sealed fluid side of the seal area arranged in a circular pattern to actively draw the sealed fluid onto the seal area, and with multiple dimples being narrow grooves inclined toward the atmosphere side of the seal area arranged in a circular pattern to push back the fluid toward the sealed fluid side via the pumping effect, presents a problem in that too strong a pumping effect of the dimples on the sealed fluid side increases the amount of leakage, while too strong a pumping effect of the dimples on the atmosphere side drains the sealed fluid from the seal area, thereby causing the dimples formed on the seal area to directly contact the mating sealing face to increase the torque, while causing the dimples to gradually wear and leading to loss of pumping effect.